The objective of this program is to apply proprietary bonded piezoelectric composite multilayer technology to a variety of ultrasound arrays for both imaging and therapy, which are currently limited in their ability to deliver acoustic power to the human body. Focus areas include: 1) conventional imaging arrays which are limited by probe heating, particularly in Doppler and Harmonics mode; 2) arrays to enable acoustic radiation force impulse (ARFI) imaging to operate in real-time (e.g. 2 to 10 frames / sec); and 3) arrays for improved high intensity focused ultrasound (HIFU) thermal therapy and dual-use ultrasound guidance of HIFU therapy. Because multilayers can result in matched electrical impedance between the probe and electronics without the need for transformers, it is particularly useful for clinical applications where the probe size is strictly limited, e.g. intracavity, laproscopic, and catheter-based procedures. Phase I has demonstrated the potential of PZT multilayers to operate under high power while maintaining the bandwidth and sensitivity of conventional probes designed exclusively for imaging. The feasibility of applying multilayer technology to matrix arrays (matrix multilayers) opens additional opportunities for devices with adjustable elevation aperture, focus, or steering, to effectively image and treat volumes without mechanical movement of the device, i.e. fully electronic arrays. In Phase II prototype devices will be built in each of the target areas, first in the form of multilayer 1-D arrays operating from 1 to 4 MHz. Process refinements will result in 1-D multilayers operating at higher frequencies, and matrix multilayers applied to 1.25-D to 1.75-D arrays. The development of transducer specifications and the characterization of prototypes will be carried out at Tetrad with input from researchers at Duke and Harvard Universities. A mix of commercial products and research tools will be developed under this program, and the technology should enable more rapid development and ultimately commercialization of new imaging and therapy modes which will depend on the availability of high power arrays also capable of diagnostic quality imaging.